CN111082931B - Quantum communication optical path system and quantum communication method - Google Patents
Quantum communication optical path system and quantum communication method Download PDFInfo
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- CN111082931B CN111082931B CN201911335695.8A CN201911335695A CN111082931B CN 111082931 B CN111082931 B CN 111082931B CN 201911335695 A CN201911335695 A CN 201911335695A CN 111082931 B CN111082931 B CN 111082931B
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
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- H04L9/00—Cryptographic mechanisms or cryptographic arrangements for secret or secure communications; Network security protocols
- H04L9/08—Key distribution or management, e.g. generation, sharing or updating, of cryptographic keys or passwords
- H04L9/0816—Key establishment, i.e. cryptographic processes or cryptographic protocols whereby a shared secret becomes available to two or more parties, for subsequent use
- H04L9/0852—Quantum cryptography
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- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
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- H04B10/506—Multiwavelength transmitters
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
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Abstract
The application provides a quantum communication optical path system and a quantum communication method. The optical signal (namely the first detection optical signal pulse and the second detection optical signal pulse) can directly reach the PMI polarization-maintaining interference ring by bypassing the phase intensity modulation module (the intensity modulator and the phase modulator) through the first polarization beam splitter, so that the problem of optical signal loop series mode is solved, and the modulation speed of the circuit is greatly improved.
Description
Technical Field
The present application relates to the field of quantum communication, and in particular, to a quantum communication optical path system and a quantum communication method.
Background
Quantum communication is a novel communication mode for information transmission by using quantum entanglement effect. In the quantum secure communication technology, the most commonly used encoding methods are phase encoding and polarization encoding. Among them, quantum communication based on phase encoding is a secure communication method that can stably transmit in an optical fiber.
The two-way quantum communication in the quantum communication optical path system needs to return an optical signal along the original path to perform decoding operation. However, in the conventional optical path system for quantum communication, during the transmission of optical signals, the electro-optical modulator may interfere with the optical signals in the loop, thereby causing the problem of the optical signal loop crosstalk in the two-way quantum communication system.
Disclosure of Invention
Based on this, it is necessary to provide a quantum communication optical path system and a quantum communication method for solving the problem of the optical signal loop serial mode in the conventional quantum communication optical path system.
The application provides a quantum communication optical path system. The quantum communication optical path system comprises a light source module, an intensity polarization modulation module, a polarization-maintaining interference ring, a phase intensity modulation module, a first isolator, a first polarization beam splitter, a second isolator, a beam splitter, a second polarization beam splitter, a 90-degree Faraday rotator and a second phase modulator. The input end of the intensity polarization modulation module is connected with the output end of the light source module and is used for carrying out intensity modulation and polarization modulation on the optical signal pulse. And the first end of the polarization-maintaining interference ring is connected with the output end of the intensity polarization modulation module. The input end of the phase intensity modulation module is connected with the third end of the polarization-maintaining interference ring and is used for carrying out phase modulation and intensity modulation on the optical signal pulse passing through the polarization-maintaining interference ring. The input end of the first isolator is connected with the output end of the phase intensity modulation module. And the first end of the first polarization beam splitter is connected with the output end of the first isolator. The input end of the second isolator is connected with the third end of the first polarization beam splitter, and the output end of the second isolator is connected with the fourth end of the polarization-maintaining interference ring.
The first end of the beam splitter is connected with the second end of the first polarization beam splitter through a communication channel. And the first end of the second polarization beam splitter is connected with the third end of the beam splitter. The second phase modulator first end is connected with the second polarization beam splitter second end. And a first end of the 90 DEG Faraday rotator mirror is connected with a second end of the second phase modulator. And the second end of the 90-degree Faraday rotator mirror is connected with the third end of the second polarization beam splitter.
The application provides the quantum communication optical path system and the quantum communication method. Through the quantum communication optical path system, an optical signal pulse is emitted by a Bob end light source, and is divided into a front pulse and a rear pulse by the PMI polarization-maintaining interference ring after intensity and polarization modulation, namely, the first optical signal pulse is a front pulse, and the second optical signal pulse is a rear pulse. The first optical signal pulse (front pulse) and the second optical signal pulse (back pulse) are phase-modulated and intensity-modulated by the phase intensity modulation module, which can be understood as preprocessing of the pulse signals. And then transmitted to the Alice terminal via the communication channel.
After the first optical signal pulse (front pulse) and the second optical signal pulse (rear pulse) which are subjected to phase modulation and intensity modulation reach the Alice end, part of optical signals (namely the first detection optical signal and the third detection optical signal) are separated through a beam splitter, and safety detection is performed. The remaining optical signals (i.e., the second optical signal and the fourth optical signal) are subjected to phase encoding operation by the second polarization beam splitter in different directions in a loop (a loop formed by the second phase modulator, the second polarization beam splitter and the 90 ° faraday rotator) through the faraday rotator and the electro-optical phase modulator, so as to form a first probe optical signal pulse and a second probe optical signal pulse, and then are transmitted to the Bob terminal through the communication channel.
After the first detection optical signal pulse and the second detection optical signal pulse reach the Bob end, the first detection optical signal pulse and the second detection optical signal pulse bypass a phase intensity modulation module (an intensity modulator and a phase modulator) through a first polarization beam splitter and directly reach the PMI polarization maintaining interference ring. According to the difference between the phase premodulation of the Bob end and the phase encoding of the Alice end, the first detection optical signal pulse and the second detection optical signal pulse can be emitted from the first end (port 1) or the second end (port 2) of the PMI polarization-maintaining interference ring to reach different single photon detectors. At the moment, the Bob end can reversely solve the code of the Alice end on the optical pulse according to the response of different single-photon detectors and the premodulation of the optical pulse, so that the quantum communication is realized.
Therefore, the Alice end is encoded by the second polarization beam splitter from two directions along a loop through the electro-optic phase modulator simultaneously, and the polarization of the optical signals (namely the first detection optical signal pulse and the second detection optical signal pulse) returning to the Bob end through the communication channel just differs from the polarization emitted from the Bob end by an angle of 90 degrees under the action of the second polarization beam splitter and the 90-degree Faraday rotator, so that the optical signals (namely the first detection optical signal pulse and the second detection optical signal pulse) can directly reach the PMI polarization-maintaining interference ring by bypassing the phase intensity modulation module (the intensity modulator and the phase modulator) through the first polarization beam splitter, the problem of optical signal loop series mode is solved, and the modulation speed of the circuit is greatly improved.
Drawings
Fig. 1 is a schematic diagram of a quantum communication optical path system provided in the present application;
fig. 2 is a schematic diagram of an optical signal trend of a quantum communication optical path system provided in the present application;
fig. 3 is a schematic diagram of optical signal transformation of a quantum communication optical path system provided in the present application;
fig. 4 is a schematic diagram of an optical signal after being pre-modulated in the quantum communication optical path system provided by the present application.
Description of the reference numerals
The system comprises a quantum communication optical path system 100, a light source module 110, an intensity polarization modulation module 120, a polarization-maintaining interference ring 140, a phase intensity modulation module 150, a first isolator 170, a first polarization beam splitter 180, a second isolator 190, a beam splitter 210, a second polarization beam splitter 220, a second phase modulator 240, a 90-degree Faraday rotator 230, a first single-photon detector 141, a second single-photon detector 250, an optical circulator 130, a third single-photon detector 131, an adjustable attenuator 121, a polarization modulator 122, a third polarization beam splitter 123, a first phase modulator 151 and an intensity modulator 152.
Detailed Description
In order to make the objects, technical solutions and advantages of the present application more apparent, the present application is further described in detail below by way of embodiments and with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative of the present application and are not intended to limit the present application.
The numbering of the components as such, e.g., "first", "second", etc., is used herein only to distinguish the objects as described, and does not have any sequential or technical meaning. The term "connected" and "coupled" when used in this application, unless otherwise indicated, includes both direct and indirect connections (couplings). In the description of the present application, it is to be understood that the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", and the like, indicate orientations or positional relationships based on those shown in the drawings, and are used only for convenience in describing the present application and for simplicity in description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed in a particular orientation, and be operated, and thus, are not to be considered as limiting the present application.
In this application, unless expressly stated or limited otherwise, the first feature "on" or "under" the second feature may be directly contacting the first and second features or indirectly contacting the first and second features through intervening media. Also, a first feature "on," "over," and "above" a second feature may be directly or diagonally above the second feature, or may simply indicate that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature may be directly under or obliquely under the first feature, or may simply mean that the first feature is at a lesser elevation than the second feature.
Referring to fig. 1-3, the present application provides a quantum communication optical path system 100. The quantum communication optical path system 100 includes an optical source module 110, an intensity polarization modulation module 120, a polarization-maintaining interference ring 140, a phase intensity modulation module 150, a first isolator 170, a first polarization beam splitter 180, a second isolator 190, a beam splitter 210, a second polarization beam splitter 220, a 90 ° faraday mirror 230, and a second phase modulator 240. The input end of the intensity polarization modulation module 120 is connected to the output end of the light source module 110, and is configured to perform intensity modulation and polarization modulation on the optical signal pulse. The first end of the polarization-maintaining interference ring 140 is connected to the output end of the intensity polarization modulation module 120. The input end of the phase intensity modulation module 150 is connected to the third end of the polarization-maintaining interferometric ring 140, and is configured to perform phase modulation and intensity modulation on the optical signal pulse passing through the polarization-maintaining interferometric ring 140. The input end of the first isolator 170 is connected to the output end of the phase intensity modulation module 150. The first end of the first polarization beam splitter 180 is connected to the output end of the first isolator 170. The input end of the second isolator 190 is connected to the third end of the first polarization beam splitter 180, and the output end of the second isolator 190 is connected to the fourth end of the polarization maintaining interference ring 140.
The first end of the beam splitter 210 is connected to the second end of the first polarization beam splitter 180 via a communication channel. The first end of the second polarization beam splitter 220 is connected to the third end of the beam splitter 210. The first end of the second phase modulator 240 is connected to the second end of the second polarization beam splitter 220. A first terminal of the 90 ° faraday rotator 230 is connected to a second terminal of the second phase modulator 240. The second end of the 90 ° faraday rotator 230 is connected to the third end of the second polarization beam splitter 220.
In this embodiment, the light source module 110 is configured to emit light signal pulses at a receiving end (Bob end). The input end of the intensity polarization modulation module 120 is connected to the output end of the light source module 110, and is configured to perform intensity modulation and polarization modulation on the optical signal pulse. A first end of the polarization-maintaining interference ring 140 is connected to the output end of the intensity polarization modulation module 120, and is configured to divide the optical signal pulse passing through the intensity polarization modulation module 120 into a first optical signal pulse and a second optical signal pulse. The second optical signal pulse has a time delay relative to the first optical signal pulse. The input end of the phase intensity modulation module 150 is connected to the third end of the polarization maintaining interferometric ring 140, and is configured to perform phase modulation and intensity modulation on the first optical signal pulse and the second optical signal pulse, respectively. The input end of the first isolator 170 is connected to the output end of the phase intensity modulation module 150, and is configured to block transmission directions of the first optical signal pulse and the second optical signal pulse that are subjected to intensity modulation, so that an optical path can pass through only one direction.
The first optical signal pulse and the second optical signal pulse passing through the first isolator 170 pass through the first polarization beam splitter 180 in a single direction, and then are transmitted to a beam splitter 210 at a transmitting end (Alice end) through a channel. The first end of the beam splitter 210 is connected to the second end of the first polarization beam splitter 180, and is configured to divide the first optical signal pulse transmitted through the channel after passing through the polarization beam splitter 180 into a first detection optical signal and a second optical signal, and divide the second optical signal pulse transmitted through the channel after passing through the polarization beam splitter 180 into a third detection optical signal and a fourth optical signal.
The first end of the second polarization beam splitter 220 is connected to the third end of the beam splitter 210, and is configured to split the second optical signal into two second sub optical signals. The fourth optical signal is split into two fourth sub-optical signals. One of the two second sub optical signals sequentially passes through the second phase modulator 240 and the 90 ° faraday rotator 230 and then is transmitted to the third end of the second polarization beam splitter 220, so as to form a first sub detection optical signal. Another second sub optical signal sequentially passes through the 90 ° faraday rotator 230 and the second phase modulator 240 and then is transmitted to the second end of the second polarization beam splitter 220, so as to form a second sub detection optical signal. The first sub detection optical signal and the second sub detection optical signal are combined into a first detection optical signal pulse after passing through the second polarization beam splitter 220.
One of the two fourth sub optical signals sequentially passes through the second phase modulator 240 and the 90 ° faraday rotator 230 and then is transmitted to the third end of the second polarization beam splitter 220, so as to form a third sub detection optical signal. Another fourth sub optical signal passes through the 90 ° faraday rotator 230 and the second phase modulator 240 and then is transmitted to the second end of the second polarization beam splitter 220, so as to form a fourth sub detection optical signal. The third sub detection optical signal and the fourth sub detection optical signal are combined into a second detection optical signal pulse by the second polarization beam splitter 220.
The first detection light signal pulse passes through the beam splitter 210, is transmitted to the second end of the first polarization beam splitter 180 through a channel, and is transmitted to the polarization-maintaining interference ring 140 through the first polarization beam splitter 180 and the second isolator 190 for detection.
The second detection light signal pulse passes through the beam splitter 210, is transmitted to the second end of the first polarization beam splitter 180 through a channel, and is transmitted to the polarization-maintaining interference ring 140 through the first polarization beam splitter 180 and the second isolator 190 for detection.
The second isolator 190 is configured to block a transmission direction, so that the optical path can pass through only one direction.
Therefore, through the quantum communication optical path system 100, the optical signal pulse is emitted from the Bob-side light source, and after intensity and polarization modulation, the optical signal pulse is divided into two front and rear pulses by the PMI polarization maintaining interference ring 140, that is, the first optical signal pulse is a front pulse, and the second optical signal pulse is a rear pulse. The first optical signal pulse (front pulse) and the second optical signal pulse (back pulse) are phase-modulated and intensity-modulated by the phase intensity modulation module 150, which can be understood as the preprocessing of the pulse signals. And then transmitted to the Alice terminal via the communication channel.
After the first optical signal pulse (front pulse) and the second optical signal pulse (rear pulse) which are subjected to phase modulation and intensity modulation reach the Alice terminal, a part of optical signals (namely, the first detection optical signal and the third detection optical signal) are separated through the beam splitter 210, and security detection is performed. The remaining optical signals (i.e., the second optical signal and the fourth optical signal) are subjected to a phase encoding operation by the second polarization beam splitter 220 in a different direction in a loop (a loop formed by the second phase modulator 240, the second polarization beam splitter 220, and the 90 ° faraday rotator 230) through the faraday rotator and the electro-optical phase modulator, so as to form a first probe optical signal pulse and a second probe optical signal pulse, and then are transmitted to the Bob terminal through the communication channel.
After the first probe optical signal pulse and the second probe optical signal pulse reach Bob, they may bypass the phase intensity modulation module 150 (the intensity modulator 152 and the phase modulator 151) via the first polarization beam splitter 180 and directly reach the PMI polarization maintaining interferometric ring 140. According to the difference between the phase premodulation of the Bob end and the phase encoding of the Alice end, the first detection optical signal pulse and the second detection optical signal pulse are emitted from the first end (port 1) or the second end (port 2) of the PMI polarization maintaining interference ring 140 to reach different single photon detectors. At the moment, the Bob end can reversely solve the code of the Alice end on the optical pulse according to the response of different single-photon detectors and the premodulation of the optical pulse, so that the quantum communication is realized.
Therefore, the Alice end passes through the second polarization beam splitter 220 from two directions through the electro-optical phase modulator 240 to perform encoding simultaneously along a loop, and the polarization of the optical signals (i.e. the first probe optical signal pulse and the second probe optical signal pulse) returning to the Bob end through the communication channel just differs from the polarization of the optical signals exiting from the Bob end by an angle of 90 ° through the actions of the second polarization beam splitter 220 and the 90 ° faraday rotator 230, so that the optical signals (i.e. the first probe optical signal pulse and the second probe optical signal pulse) can directly reach the polarization-maintaining interferometric ring 140 by bypassing the phase intensity modulation module 150 (the intensity modulator 152 and the phase modulator 151) through the first polarization beam splitter 180, thereby solving the problem of the PMI loop serial mode of the optical signals and greatly improving the modulation speed of the circuit.
In one embodiment, the quantum communication optical path system 100 further includes a first single-photon detector 141, a second single-photon detector 250, an optical circulator 130, and a third single-photon detector 131. The first single-photon detector 141 is connected with the second end of the polarization-maintaining interference ring 140. The second single-photon detector 250 is connected to a second end of the beam splitter 210. The first end of the optical circulator 130 is connected to the output end of the intensity polarization modulation module 120, and the second end of the optical circulator 130 is connected to the first end of the polarization maintaining interference ring 140. The third single-photon detector 131 is connected with the third end of the optical circulator 130.
In this embodiment, the first single-photon detector 141, the second single-photon detector 250, and the third single-photon detector 131 are used for APD detection. The second single-photon detector 250 is connected to the second end of the beam splitter 210, and is configured to perform security detection on a part of optical signals transmitted to the Alice end by the optical signal at the Bob end via a communication channel and split by the beam splitter 210. The first single-photon detector 141 is connected with the second end of the polarization-maintaining interference ring 140, and the third single-photon detector 131 is connected with the third end of the optical circulator 130. The first single-photon detector 141 and the third single-photon detector 131 are configured to detect an optical signal emitted from the first port or the second port after an optical signal at an Alice end is transmitted to the Bob end via a communication channel, and after the optical signal bypasses the phase intensity modulation module 150 (the intensity modulator 152 and the phase modulator 151) and directly reaches the PMI polarization maintaining interference ring 140.
At this time, the security detection of the quantum communication optical path system 100 is performed at the Alice side, and the decoding and the security volume analysis are performed at the Bob side. The particle number of the front pulse and the back pulse of the optical signal is used as an orthogonal basis vector for detecting safety, and the relative phase of the front pulse and the back pulse is used as a carrier for loading codes.
In one embodiment, the intensity polarization modulation module 120 includes an adjustable attenuator 121, a polarization modulator 122, and a third polarization beam splitter 123. The input end of the adjustable attenuator 121 is connected to the output end of the light source module 110. The input of the polarization modulator 122 is connected to the output of the adjustable attenuator 121. The input end of the third polarization beam splitter 123 is connected to the output end of the polarization modulator 122. The output end of the third polarization beam splitter 123 is connected to the first end of the optical circulator 130.
The Variable optical attenuator 121 (VOA) implements real-time control of signals by attenuating transmission optical power. The polarization modulator 122(PC) may implement polarization modulation of light.
In one embodiment, the phase intensity modulation module 150 includes a first phase modulator 151 and an intensity modulator 152. The input end of the first phase modulator 151 is connected to the third end of the polarization-maintaining interferometric ring 140. The input of the intensity modulator 152 is connected to the output of the first phase modulator 151.
In one embodiment, the quantum communication optical path system 100 further comprises a polarization maintaining fiber. The light source module 110, the intensity polarization modulation module 120, the polarization-maintaining interference ring 140, the phase intensity modulation module 150, the first isolator 170, and the first polarization beam splitter 180 are connected by the polarization-maintaining optical fiber.
Referring to fig. 2-3, in one embodiment, the present application provides a quantum communication method, comprising:
s10, providing an optical signal pulse by a receiving end, and carrying out intensity modulation and polarization modulation on the optical signal pulse;
s20, dividing the optical signal pulse after intensity modulation and polarization modulation into a first optical signal pulse and a second optical signal pulse, where the second optical signal pulse has a time delay relative to the first optical signal pulse;
s30, respectively performing phase modulation and intensity modulation on the first optical signal pulse and the second optical signal pulse, and transmitting the first optical signal pulse and the second optical signal pulse after the phase modulation and the intensity modulation to a transmitting end through a communication channel;
s40, dividing the first optical signal pulse transmitted to the transmitting end into a first optical signal and a second optical signal, and dividing the second optical signal pulse transmitted to the transmitting end into a third optical signal and a fourth optical signal;
s50, performing security detection according to the first detection optical signal, and dividing the second optical signal into two second sub optical signals;
s60, performing security detection according to the third detected optical signal, and dividing the fourth optical signal into two fourth sub optical signals;
s70, sequentially performing phase modulation and polarization rotation by 90 ° on one of the two second sub optical signals to form a first sub detection optical signal, sequentially performing polarization rotation by 90 ° and phase modulation on the other second sub optical signal to form a second sub detection optical signal, and combining the first sub detection optical signal and the second sub detection optical signal into a first detection optical signal pulse;
s80, sequentially performing phase modulation and polarization rotation by 90 ° on one of the two fourth sub optical signals to form a third sub detection optical signal, sequentially performing polarization rotation by 90 ° and phase modulation on the other fourth sub optical signal to form a fourth sub detection optical signal, and combining the third sub detection optical signal and the fourth sub detection optical signal to form a second detection optical signal pulse;
s90, transmitting the first probe optical signal pulse and the second probe optical signal pulse to a receiving end through a communication channel for probing, and inversely decoding the coded modulation performed by the transmitting end.
In S10, an optical signal pulse may be emitted by triggering at Bob via a pulsed laser at a repetition rate of 32 MHz. And simultaneously acquiring a trigger signal as a trigger clock signal of an electro-optical modulator and a single photon detector at Bob end. After the optical signal pulse sequentially passes through the adjustable attenuator 121, the polarization modulator 122, and the third polarization beam splitter 123, the intensity modulation and the polarization modulation are performed on the optical signal pulse.
In S20, the optical signal pulse after passing through the third polarization beam splitter 123 is modulated by a polarization maintaining interference loop 140(PMI) having an arm length difference of 3 m into front and rear pulses having a front and rear time difference of about 15 nsec, that is, the first optical signal pulse and the second optical signal pulse. At this time, the second optical signal pulse has a time delay with respect to the first optical signal pulse. And, wherein PMFC in said polarization maintaining interferometric ring 140(PMI) is 50: 50 beam splitter.
In S30, the first optical signal pulse and the second optical signal pulse are modulated by the intensity modulator 152 according to the desired pre-processing. Specifically, the required pretreatments may be constant intensity, halved intensity, complete extinction, and the like, respectively. Accordingly, the first optical signal pulse is eliminated, the second optical signal pulse remains unchanged, and the corresponding information is encoded as 0. Or, the second optical signal pulse is eliminated, the first optical signal pulse is unchanged, and the corresponding information is coded to be 1. Or, half of the light intensity of the first optical signal pulse is eliminated, half of the light intensity of the second optical signal pulse is eliminated, and the corresponding information code is 0.
Then, the first optical signal pulse and the second optical signal pulse are modulated by the first phase modulator 151 according to the desired pre-processing. Specifically, the required pre-processing may be changing the Π phase and not changing the phase, respectively. Accordingly, the phase of the second optical signal pulse remains unchanged, i.e. the phase is not changed, and the corresponding information is encoded as 0. Or the first optical signal pulse changes pi phase or the second optical signal pulse changes pi phase, that is, changes relative phase, and the corresponding information is encoded as 1.
The first optical signal pulse and the second optical signal pulse are pre-modulated into front and rear pulses at the Bob end, have adjustable relative phases, and are transmitted to a transmitting end (Alice end) through a communication channel.
In S40, the first optical signal pulse transmitted to Alice is divided into a first detection optical signal and a second optical signal by the beam splitter 210. The second optical signal pulse is split into a third optical signal and a fourth optical signal. At this time, a part of the optical signals (the first detection optical signal and the third detection optical signal) is split by the beam splitter 210, and the detection signals (the first detection optical signal and the third detection optical signal) are detected by the single photon detector 250 for security, and the trigger signal is always synchronized with the phase modulator at Alice as a clock signal.
In the S50 and S60, the second optical signal is split into two second sub optical signals by the second polarization beam splitter 220. The fourth optical signal is split into two fourth sub-optical signals.
In S70, one of the two second sub optical signals is sequentially phase-modulated and polarization-rotated by 90 ° to form a first sub probe optical signal. And the other second sub optical signal is subjected to polarization state rotation of 90 degrees and phase modulation in sequence to form a second sub detection optical signal. And combining the first sub-probe optical signal and the second sub-probe optical signal into a first probe optical signal pulse.
In S80, one of the two fourth sub optical signals is sequentially phase-modulated and polarization-rotated by 90 ° to form a third sub probe optical signal. And the other fourth sub optical signal is subjected to polarization state rotation by 90 degrees and phase modulation in sequence to form a fourth sub detection optical signal, and the third sub detection optical signal and the fourth sub detection optical signal are combined into a second detection optical signal pulse.
The phase of the two second sub optical signals is kept unchanged during the phase modulation by the second phase modulator 240. Or changing the pi phase of the two second sub optical signals. At this time, the first optical signal pulse transmitted to Alice end is divided by the beam splitter 210 into two second optical sub-signals. The corresponding information code is 0 without changing the phase, and the corresponding information code is 1 with changing the pi phase.
The phases of the two fourth sub optical signals are kept unchanged during the phase modulation by the second phase modulator 240. Or, changing pi phase of two fourth sub optical signals. At this time, the second optical signal pulse transmitted to the Alice end is divided by the beam splitter 210 to obtain the remaining light, i.e., two fourth optical sub-signals. The corresponding information code is 0 without changing the phase, and the corresponding information code is 1 with changing the pi phase.
Therefore, the front and rear pulses (the first optical signal pulse and the second optical signal pulse) transmitted to the Alice end are subjected to two kinds of modulation of the relative phases through the loop formed by the second phase modulator 240, the second polarization beam splitter 220, and the 90 ° faraday mirror 230.
At this time, the remaining optical signals are subjected to a phase encoding operation in a loop (a loop formed by the second phase modulator 240, the second polarization beam splitter 220, and the 90 ° faraday rotator 230) in different directions through the faraday rotator and the electro-optical phase modulator. After being looped, the first and second probe optical signal pulses are formed after being combined by the second polarization beam splitter 220. And transmitting the first probe optical signal pulse and the second probe optical signal pulse to Bob via a communication channel.
In S90, after the first probe optical signal pulse and the second probe optical signal pulse are transmitted to a receiving end (Bob end) through a communication channel, the first polarization beam splitter 180 bypasses the intensity modulator 152 and the phase modulator 151 to directly reach the PMI polarization maintaining interferometric ring 140. In the PMI polarization maintaining interference ring 140, the first PMFC divides the first probe optical signal pulse and the second probe optical signal pulse (front and rear pulses) returning through the Alice end into two paths, and the first probe optical signal pulse (front pulse) and the second probe optical signal pulse (rear pulse) passing through the optical fiber with more than 3 meters reach the second PMFC at the same time. At this time, according to the relative phase 0 or Π of the first detection optical signal pulse (front pulse) and the second detection optical signal pulse (rear pulse), all paths of interference are cancelled or enhanced, and all paths of interference are enhanced or cancelled at the outlet (port 1 or port 2). Therefore, according to the difference between the phase premodulation at Bob end and the phase encoding at Alice end, the first probe optical signal pulse and the second probe optical signal pulse will exit from the first end (port 1) or the second end (port 2) of the PMI polarization maintaining interference ring 140 to reach different single photon detectors.
At this time, it can be understood that: the corresponding information code is 0 or the corresponding information code is 1, and the corresponding information code is emitted from the port 1 or the port 2 and reaches the corresponding third single-photon detector 131 and the corresponding first single-photon detector 141 for detection. Meanwhile, at the Bob end, according to the responses of the third single-photon detector 131 and the first single-photon detector 141 and the pre-modulation of the optical pulse at the Bob end, the xor calculation is performed on the information corresponding to the third single-photon detector and the first single-photon detector 141, and the encoding of the optical pulse at the Alice end can be solved reversely, so that the quantum communication is realized.
In one embodiment, the above steps S10-S90 are repeated at a repetition frequency of 32MHz, and communication is performed for a period of time, and the results detected by the detectors are recorded by both Alice and Bob. According to the premodulation and time position of the corresponding detection signal published by the Bob end and the premodulation and detection result of a part of coding signal, the Alice end publishes the detection result of the corresponding detection signal and the modulation information code of the coding signal of the corresponding time position, the two sides can calculate the safety capacity of the channel, and finally the secret key is successfully shared according to the secret key extraction mode agreed in advance.
Therefore, the problems of high bit error rate, real-time compensation and loop burst mode in a series of quantum communication protocols can be solved through the quantum communication optical path system 100 and the quantum communication method in the above embodiments, so that the quantum communication system can operate more stably, accurately and at high speed. Meanwhile, as a new optical path system developed by a quantum secure direct communication DL04 protocol, the quantum communication optical path system 100 can realize deterministic key transmission and direct transmission of information in quantum lines.
Referring to fig. 4, in an embodiment, a diagram of an optical signal after pre-modulation is shown through a quantum communication optical path system. At this time, after the pre-modulation, the optical signal quantum state is as shown in fig. 4, and the detected Bit (Test Bit) is divided into only the front pulse s and only the rear pulse l. The Signal Bit (Signal Bit) is that the intensity of the front pulse s and the rear pulse l becomes half of the original intensity, and the relative phase theta can be 0 and pi respectively.
The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only express several embodiments of the present application, and the description thereof is more specific and detailed, but not construed as limiting the scope of the present application. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the concept of the present application, which falls within the scope of protection of the present application. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (11)
1. A quantum communication optical path system, comprising:
a light source module (110);
the input end of the intensity polarization modulation module (120) is connected with the output end of the light source module (110);
a polarization-maintaining interference ring (140), wherein a first end of the polarization-maintaining interference ring (140) is connected with an output end of the intensity polarization modulation module (120);
the input end of the phase intensity modulation module (150) is connected with the third end of the polarization-maintaining interference ring (140);
a first isolator (170), an input of the first isolator (170) being connected to an output of the phase intensity modulation module (150);
a first polarization beam splitter (180), a first end of the first polarization beam splitter (180) being connected to an output end of the first isolator (170);
a second isolator (190), wherein the input end of the second isolator (190) is connected with the third end of the first polarization beam splitter (180), and the output end of the second isolator (190) is connected with the fourth end of the polarization-maintaining interference ring (140);
a beam splitter (210), a first end of the beam splitter (210) and a second end of the first polarization beam splitter (180) being connected by a communication channel;
a second polarization beam splitter (220), wherein a first end of the second polarization beam splitter (220) is connected with a third end of the beam splitter (210);
a second phase modulator (240), said second phase modulator (240) having a first end connected to said second polarizing beamsplitter (220) second end;
a 90 DEG Faraday rotator (230), wherein a first end of the 90 DEG Faraday rotator (230) is connected with a second end of the second phase modulator (240), and a second end of the 90 DEG Faraday rotator (230) is connected with a third end of the second polarization beam splitter (220);
the light source module (110) provides light signal pulses, and the intensity polarization modulation module (120) performs intensity modulation and polarization modulation on the light signal pulses;
the polarization-preserving interference ring (140) splits the intensity-modulated and polarization-modulated optical signal pulses into first optical signal pulses and second optical signal pulses, the second optical signal pulses having a time delay relative to the first optical signal pulses;
the phase intensity modulation module (150) respectively performs phase modulation and intensity modulation on the first optical signal pulse and the second optical signal pulse;
the first optical signal pulse and the second optical signal pulse which are subjected to phase modulation and intensity modulation sequentially pass through the first isolator (170) and the first polarization beam splitter (180), and are transmitted to a transmitting end through a communication channel;
the beam splitter (210) splits the first optical signal pulse transmitted to the transmitting end into a first optical signal and a second optical signal, and splits the second optical signal pulse transmitted to the transmitting end into a third optical signal and a fourth optical signal;
the second polarization beam splitter (220) splits the second optical signal into two second sub optical signals and splits the fourth optical signal into two fourth sub optical signals;
one of the two second sub optical signals sequentially passes through the second phase modulator (240) and the 90 DEG Faraday rotator mirror (230) to form a first sub detection optical signal; another second sub optical signal sequentially passes through the 90 DEG Faraday rotator (230) and the second phase modulator (240) to form a second sub probe optical signal; the first sub detection optical signal and the second sub detection optical signal are combined into a first detection optical signal pulse after passing through the second polarization beam splitter (220);
one of the two fourth sub optical signals sequentially passes through the second phase modulator (240) and the 90-degree Faraday rotator (230) to form a third sub detection optical signal; another fourth sub optical signal sequentially passes through the 90 DEG Faraday rotator (230) and the second phase modulator (240) to form a fourth sub probe optical signal; the third sub detection optical signal and the fourth sub detection optical signal are combined into a second detection optical signal pulse after passing through the second polarization beam splitter (220);
the first detection light signal pulse is transmitted to the second end of the first polarization beam splitter (180) through a communication channel after passing through the beam splitter (210), and is transmitted to the polarization-preserving interference ring (140) for detection through the first polarization beam splitter (180) and the second isolator (190);
the second detection light signal pulse is transmitted to the second end of the first polarization beam splitter (180) through a communication channel after passing through the beam splitter (210), and is transmitted to the polarization-preserving interference ring (140) for detection through the first polarization beam splitter (180) and the second isolator (190).
2. The quantum communication optical circuit system of claim 1, further comprising:
and the first single-photon detector (141) is connected with the second end of the polarization-maintaining interference ring (140).
3. The quantum communication optical circuit system of claim 1, further comprising:
and the second single-photon detector (250) is connected with the second end of the beam splitter (210).
4. The quantum communication optical circuit system of claim 1, further comprising:
a first end of the optical circulator (130) is connected with the output end of the intensity polarization modulation module (120), and a second end of the optical circulator (130) is connected with a first end of the polarization-preserving interference ring (140);
and the third single-photon detector (131) is connected with the third end of the optical circulator (130).
5. The quantum communication optical path system of claim 4, wherein the intensity polarization modulation module (120) comprises:
the input end of the adjustable attenuator (121) is connected with the output end of the light source module (110);
a polarization modulator (122), wherein the input end of the polarization modulator (122) is connected with the output end of the adjustable attenuator (121);
the input end of the third polarization beam splitter (123) is connected with the output end of the polarization modulator (122), and the output end of the third polarization beam splitter (123) is connected with the first end of the optical circulator (130).
6. The quantum communication optical path system of claim 1, wherein the phase intensity modulation module (150) comprises:
a first phase modulator (151), wherein the input end of the first phase modulator (151) is connected with the third end of the polarization-maintaining interference ring (140);
an intensity modulator (152), the intensity modulator (152) input being connected to the first phase modulator (151) output.
7. The quantum communication optical path system according to claim 1, further comprising a polarization-maintaining optical fiber, wherein the light source module (110), the intensity polarization modulation module (120), the polarization-maintaining interference ring (140), the phase intensity modulation module (150), the first isolator (170), and the first polarization beam splitter (180) are connected via the polarization-maintaining optical fiber.
8. A quantum communication method, comprising:
s10, providing an optical signal pulse by a receiving end, and carrying out intensity modulation and polarization modulation on the optical signal pulse;
s20, dividing the optical signal pulse after intensity modulation and polarization modulation into a first optical signal pulse and a second optical signal pulse, where the second optical signal pulse has a time delay relative to the first optical signal pulse;
s30, respectively performing phase modulation and intensity modulation on the first optical signal pulse and the second optical signal pulse, and transmitting the first optical signal pulse and the second optical signal pulse after the phase modulation and the intensity modulation to a transmitting end through a communication channel;
s40, dividing the first optical signal pulse transmitted to the transmitting end into a first optical signal and a second optical signal, and dividing the second optical signal pulse transmitted to the transmitting end into a third optical signal and a fourth optical signal;
s50, performing security detection according to the first detection optical signal, and dividing the second optical signal into two second sub optical signals;
s60, performing security detection according to the third detected optical signal, and dividing the fourth optical signal into two fourth sub optical signals;
s70, sequentially performing phase modulation and polarization rotation by 90 ° on one of the two second sub optical signals to form a first sub detection optical signal, sequentially performing polarization rotation by 90 ° and phase modulation on the other second sub optical signal to form a second sub detection optical signal, and combining the first sub detection optical signal and the second sub detection optical signal into a first detection optical signal pulse;
s80, sequentially performing phase modulation and polarization rotation by 90 ° on one of the two fourth sub optical signals to form a third sub detection optical signal, sequentially performing polarization rotation by 90 ° and phase modulation on the other fourth sub optical signal to form a fourth sub detection optical signal, and combining the third sub detection optical signal and the fourth sub detection optical signal to form a second detection optical signal pulse;
s90, transmitting the first probe optical signal pulse and the second probe optical signal pulse to a receiving end through a communication channel for probing, and inversely decoding the coded modulation performed by the transmitting end.
9. The quantum communication method of claim 8, wherein in the S30, intensity modulating the first optical signal pulse with the second optical signal pulse comprises:
removing the first optical signal pulse, the second optical signal pulse remaining unchanged;
or, the first optical signal pulse is kept unchanged, and the second optical signal pulse is eliminated;
or, the light intensity of the first optical signal pulse is halved, and the light intensity of the second optical signal pulse is halved.
10. The quantum communication method of claim 9, wherein in the S30, phase modulating the first optical signal pulse with the second optical signal pulse comprises:
maintaining the phase of the second optical signal pulse unchanged;
or changing the pi phase of the first optical signal pulse;
or changing the pi phase of the second optical signal pulse.
11. The quantum communication method of claim 10, wherein in the S70 and S80, phase-modulating the two second sub optical signals and the two fourth sub optical signals comprises:
keeping the phase of the two second sub-optical signals unchanged;
or changing the pi phase of the two second sub optical signals;
or, the phases of the two fourth sub optical signals are kept unchanged;
or, changing pi phase of two fourth sub optical signals.
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| CN113037384A (en) * | 2021-03-08 | 2021-06-25 | 安徽问天量子科技股份有限公司 | Intensity modulation device and method |
| CN113422653B (en) * | 2021-06-18 | 2022-08-09 | 广西大学 | Quantum communication system without polarization feedback and quantum secure direct communication method |
| CN114006693B (en) * | 2021-06-30 | 2023-08-11 | 广东国腾量子科技有限公司 | Polarization coding QKD system and method based on silicon optical integrated chip |
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| CN108462576A (en) * | 2018-03-23 | 2018-08-28 | 华南师范大学 | local active phase compensation method and system |
| CN108667519A (en) * | 2017-03-28 | 2018-10-16 | 科大国盾量子技术股份有限公司 | Intensity modulated device and method and its application in quantum key distribution system |
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| CN103546280B (en) * | 2013-10-28 | 2016-07-06 | 中国科学技术大学 | Encoder for quantum cryptography communication |
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| CN108667519A (en) * | 2017-03-28 | 2018-10-16 | 科大国盾量子技术股份有限公司 | Intensity modulated device and method and its application in quantum key distribution system |
| CN108462576A (en) * | 2018-03-23 | 2018-08-28 | 华南师范大学 | local active phase compensation method and system |
| CN109708852A (en) * | 2019-01-17 | 2019-05-03 | 中国科学院武汉物理与数学研究所 | Measure the experimental provision and its method of superelevation polarization extinction ratio |
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